The present invention relates to an outer sheathed endoscope having an outer sheath for preventing a flexible insertion portion of the endoscope from being contaminated.
In endoscopy, in order to eliminate infection among patients through an endoscope, a flexible insertion portion of the endoscope is covered by an outer sheath, and the outer sheath is replaced with a new one at each endoscopy.
In order to enable a treatment tool to be used during endoscopy, a channel tube through which the treatment tool is to be passed is formed in the outer sheath, and the channel tube is passed through a guide channel disposed in the flexible insertion portion.
In such an outer sheathed endoscope, during endoscopy, it is required to prevent a tip end part of the outer sheath from being moved with respect to a tip end part of the flexible insertion portion in which an observation window and the like are disposed.
In order to comply with this, conventionally, a locking mechanism is disposed. The locking mechanism is configured by a hook mechanism for restricting the tip end part of the flexible insertion portion from rearward escaping from the tip end of the outer sheath. When the flexible insertion portion is to be pulled out from the outer sheath after endoscopy, a cap-shaped tip end member of the outer sheath is externally pressed to be elastically deformed in a radial direction, thereby disengaging the hook mechanism (for example, Patent literatures Japanese Patent Publication No. H03-193023 and Japanese Utility model Publication No. H07-33301).
When, in order to disengage the hook mechanism, the cap-shaped tip end member of the outer sheath is externally pressed to be elastically deformed, the following cases often arise. The degree of application of the pressing force is not known, and hence the disengagement cannot be well conducted. By contrast, the pressing force is excessively applied, and the tip end member of the outer sheath is broken.